Crystal Structure of FosB from Enterococcus faecium with Fosfomycin

Experimental Data Snapshot

  • Resolution: 2.00 Å
  • R-Value Free: 0.254 
  • R-Value Work: 0.213 
  • R-Value Observed: 0.216 

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Structural and functional characterization of fosfomycin resistance conferred by FosB from Enterococcus faecium.

Wiltsie, V.Travis, S.Shay, M.R.Simmons, Z.Frantom, P.Thompson, M.K.

(2022) Protein Sci 31: 580-590

  • DOI: https://doi.org/10.1002/pro.4253
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    The Gram-positive pathogen Enterococcus faecium is one of the leading causes of hospital-acquired vancomycin resistant enterococci (VRE) infections. E. faecium has extensive multidrug resistance and accounts for more than two million infections in the United States each year. FosB is a fosfomycin resistance enzyme found in Gram-positive pathogens like E. faecium. Typically, the FosB enzymes are Mn 2+ -dependent bacillithiol (BSH) transferases that inactivate fosfomycin through nucleophilic addition of the thiol to the antibiotic. However, our kinetic analysis of FosB Ef shows that the enzyme does not utilize BSH as a thiol substrate, unlike the other well characterized FosB enzymes. Here we report that FosB Ef is a Mn 2+ -dependent L-cys transferase. In addition, we have determined the three-dimensional X-ray crystal structure of FosB Ef in complex with fosfomycin at a resolution of 2.0 Å. A sequence similarity network (SSN) was generated for the FosB family to investigate the unexpected substrate selectivity. Three non-conserved residues were identified in the SSN that may contribute to the substrate selectivity differences in the family of enzymes. Our structural and functional characterization of FosB Ef establishes the enzyme as a potential target and may prove useful for future structure-based development of FosB inhibitors to increase the efficacy of fosfomycin.

  • Organizational Affiliation

    Department of Chemistry & Biochemistry, The University of Alabama, Tuscaloosa, Alabama, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Metallothiol transferase FosB
A, B
139Enterococcus faeciumMutation(s): 0 
Gene Names: fosB
Find proteins for F1C939 (Enterococcus faecium)
Explore F1C939 
Go to UniProtKB:  F1C939
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupF1C939
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 3 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
FCN (Subject of Investigation/LOI)
Query on FCN

Download Ideal Coordinates CCD File 
I [auth A],
L [auth B]
C3 H7 O4 P
Query on EDO

Download Ideal Coordinates CCD File 
D [auth A]
E [auth A]
F [auth A]
G [auth A]
H [auth A]
D [auth A],
E [auth A],
F [auth A],
G [auth A],
H [auth A],
K [auth B]
C2 H6 O2
MN (Subject of Investigation/LOI)
Query on MN

Download Ideal Coordinates CCD File 
C [auth A],
J [auth B]
Experimental Data & Validation

Experimental Data

  • Resolution: 2.00 Å
  • R-Value Free: 0.254 
  • R-Value Work: 0.213 
  • R-Value Observed: 0.216 
  • Space Group: P 41 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 79.874α = 90
b = 79.874β = 90
c = 95.639γ = 90
Software Package:
Software NamePurpose
PDB_EXTRACTdata extraction
SCALAdata scaling
CrysalisProdata reduction

Structure Validation

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Ligand Structure Quality Assessment 

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Cystic Fibrosis FoundationUnited StatesTHOMPS20I0

Revision History  (Full details and data files)

  • Version 1.0: 2022-07-27
    Type: Initial release
  • Version 1.1: 2023-10-18
    Changes: Data collection, Refinement description